Impregnated cathode

ABSTRACT

An impregnated pallet including a porous metal body to which an electron radiating material is impregnated, a cathode ring having an upper portion in which the impregnated pallet is fitted, and a cathode sleeve containing a heater therein and having a closed upper end mounted to the lower end of the cathode ring such that the closed upper end surface thereof is in close contact with the lower surface of the impregnated pallet, so as to transmit directly the heat from the heater accumulated in the cathode sleeve to the impregnated pallet. A plurality of uniformly spaced metal ribbons are formed integrally with the lower end of the cathode ring. Each metal ribbon has an end fixed to the closed upper end surface of a cathode holder. In accordance with the present invention, the impregnated cathode has an improved construction capable of shortening the video producing time and simplifying the manufacturing process, thereby improving the workability and the productivity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an impregnated cathode, and moreparticularly to an impregnated cathode with a construction comprising acathode ring having an upper end to which an impregnated pallet isfitted and a lower end to which a cathode sleeve is fitted and aplurality of metal ribbons formed integrally with the cathode ring, eachmetal ribbon having an end fixed to a cathode holder, thereby capable ofsimplifying the manufacturing process and shortening the video producingtime.

2. Description of the Prior Art

Impregnated cathodes have been mainly used in oscilloscopes whichrequire high cathode current. Recently, they have been also applied toelectron tubes which are used in televisions, since the electron tubesrequire high cathode current, according to the tendency of highresolution and large screen in televisions.

Referring to FIGS. 1A and 1B, there is shown an example of conventionalimpregnated cathode constructions. As shown in the drawings, the cathodecomprises a cylindrical cathode cup 12 made of a heat-resistant metaland closed at its lower end, an impregnated pallet 11 fitted in thecathode cup 12 and having a porous heat-resistant sintered body to whichan electron radiating material is impregnated, and a cylindrical cathodemetal sleeve 13 having a closed upper end and mounted to the cathode cup12 such that the closed upper end surface is in close contact with thelower end surface of the cathode cup 12. The cathode also comprises acylindrical cathode holder 14 surrounding the cathode sleeve 13, aplurality of metal ribbons 15 adapted to fixedly maintain the cathodesleeve 13 and the cathode holder 14 and having one end fixed to theupper end surface of the cathode sleeve 13 and the other end fixed tothe outer surface of the upper end of cathode holder, and a coil typeheater 18 adapted to heat the interior of cathode and received in thecathode holder 14 to extend into the interior of cathode sleeve 13 suchthat the outer surface thereof is uniformly spaced from the innersurface of the cathode sleeve 13, the heater having an upper end beingin contact with the inner surface of the upper end of cathode sleeve 13.

In the drawings, the reference numerals 16 and 17 designate fixing areaswhere the metal ribbons are fixed to the cathode sleeve 13 and thecathode holder 14.

Now, the operation of the conventional cathode with the above-mentionedconstruction will be described.

As a drive power is supplied to the heater 18 disposed in the cathodewhich has been assembled in an electron tube, the heater 18 emits heat,thereby causing the cathode to be heated. At this time, the heat emittedfrom the heater 18 is transmitted to the cathode cup 12, via the upperend surface of the cathode sleeve 13. The transmitted heat to thecathode cup 12 is then transmitted to the impregnated pallet 11, so thatthe impregnated pallet 11 radiates electrons, by virtue of thetransmitted heat.

In the case of the above-mentioned construction, however, there is adisadvantage of increasing the video producing time, in that the heatgenerated from the heater 18 is transmitted to the impregnated pallet11, via the closed surface of the cathode sleeve 13 and the closedsurface of the cathode cup 12. Herein, the video producing time meansthe period of from the turning-on time point of the heater 18 to thetime point that a video appears on an electron tube screen, as anelectron is radiated from the impregnated pallet 11. In making theconventional cathode with the above-mentioned construction, the cathodecup 12 and the cathode sleeve 13 should be also accord with each other,so as to improve the heat transmission efficiency. Furthermore, themetal ribbons 15 should be fixed to the upper end surface of the cathodesleeve 13 at fixing areas 16 which has been accurately predetermined onthe upper end surface. However, these works are very troublesome.

SUMMARY OF THE INVENTION

Therefore, an object of the invention is to provide an impregnatedcathode with an improved construction capable of shortening the videoproducing time and simplifying the manufacturing process by eliminatinga troublesome centering work which was required in the prior art, forcentering the cathode cup and the cathode sleeve.

In accordance with the present invention, this object can beaccomplished by providing an impregnated cathode comprising: animpregnated pallet including a porous metal body to which a materialradiating electrons upon being subjected to a heat is impregnated; acathode ring having an upper portion in which the impregnated pallet isfitted; a cathode sleeve containing a heater therein and having a closedupper end mounted to the lower end of the cathode ring such that theclosed upper end surface thereof is in close contact with the lowersurface of the impregnated pallet, so as to transmit directly the heatfrom the heater accumulated in the cathode sleeve to the impregnatedpallet; a cathode holder surrounding the cathode sleeve and having anupper end surface; and metal ribbons formed integrally with the cathodering and fixedly mounted to the upper end surface of the cathode holder.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and aspects of the invention will become apparent from thefollowing description of embodiments with reference to the accompanyingdrawings in which:

FIG. 1A is a sectional view of the construction of a conventionalimpregnated cathode;

FIG. 1B is a plan view of the conventional cathode construction;

FIG. 2A is a sectional view of a cathode with an improved constructionaccording to the present invention; and

FIG. 2B is a plan view of the cathode construction according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 2A and 2B, there is illustrated an impregnatedcathode in accordance with the present invention. As shown in thedrawings, an impregnated pallet 21 adapted to radiate electronsincluding a porous heat-resistant metal body to which an electronradiating material is impregnated, and a cathode ring 23 made of aheat-resistant metal, the impregnated pallet 1 being fixedly fitted inthe interior of the upper portion of the cathode ring 2. The cathodealso comprises a cylindrical cathode sleeve 26 adapted to transmit theheat accumulated in the interior thereof and having a closed upper end28 mounted to the lower end of the cathode ring 23 such that the closedupper end surface 28 is in direct contact with the impregnated pallet21. In the illustrated embodiment, the cathode sleeve 26 is fitted atthe upper end thereof in the lower end of the cathode ring 23. Thecathode also comprises a cylindrical cathode holder 22 surrounding thelower portion of cathode sleeve 26 such that the inner surface thereofis uniformly spaced from the outer surface of cathode sleeve 26, thecathode holder being adapted to support the construction of cathode, aplurality of metal ribbons 24 formed integrally with the lower end ofcathode ring 23 to extend downwardly and outwardly therefrom and fixedlymounted at their lower ends to the upper end surface of cathode holder22, and a heater 27 disposed in the cathode sleeve 26 and adapted toheat the cathode.

In accordance with the present invention, the cathode holder 22 isprovided at the closed surface of the upper end thereof with an openinghaving an inner surface which is in close contact with the outer surfaceof the cathode sleeve 26, upon fitting the cathode sleeve 26 in thecathode holder 22 through the opening. As above-mentioned, the ribbons24 which are uniformly spaced along the periphery of the lower end ofcathode ring 23 are fixed on the closed upper end surface of cathodeholder 22.

In FIGS. 2A and 2B, the reference numeral "25" designates fixing areaswhere respective ends of the metal ribbons 24 are fixed to the closedupper end surface of cathode holder 22.

Now, the operation of the cathode with the above-mentioned constructionaccording to the present invention will be described.

As a drive power is supplied to the heater 27, under the condition thatthe cathode has been assembled in an electron tube, the heater 27 emitsheat. The heat generated from the heater 27 is accumulated in thecathode sleeve 26 and then directly transmitted to the impregnatedpallet 21, via the closed upper end surface 28 of the cathode sleeve 26.By virtue of the transmitted heat, the impregnated pallet 21 radiateselectrons.

Since the radiation of electrons is accomplished by the heat generatedfrom the heater 27 transmitted to the impregnated pallet 21, only viathe closed upper end surface 28 of the cathode sleeve 26, the videoproducing time is considerably shortened, over the prior art wherein theradiation of electrons is accomplished by the heat generated from theheater transmitted to the impregnated pellet, via the closed surface ofthe cathode sleeve and the closed surface of the cathode cup.

The above-mentioned cathode construction of the present invention alsosolves the centering problem encountered in the prior art, in that thecathode holder 22 has the opening having an inner surface which is inclose contact with outer surface of the cathode sleeve 26 to maintainthe cathode sleeve 26 in position, upon fitting the cathode sleeve 26 inthe cathode holder 22 through the opening. In accordance with thepresent invention, the cathode construction also has the ribbons 24which are formed integrally with the lower end of cathode ring 23 andfixed on the closed upper end surface of cathode holder 22. The openingof cathode holder 22 is formed at the closed upper end surface ofcathode holder 22 on which the ribbons 24 are fixed. Accordingly, thefixing areas 25 can be easily predetermined, since the fixing of metalribbons 24 is carried out under the condition that the cathode sleeve 26has been fitted in the opening of the cathode holder 22 and maintainedin position. As a result, the workability is improved.

As apparent from the above description, the present invention providesan impregnated cathode with an improved construction capable ofshortening the video producing time and simplifying the manufacturingprocess, thereby improving the workability and the productivity.

Although the preferred embodiment of the invention have been disclosedfor illustrative purpose, those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the invention as disclosed in theaccompanying claims.

What is claimed is:
 1. An impregnated cathode comprising:an impregnatedpallet including a porous metal body to which a material radiatingelectrons upon being subjected to a heat is impregnated; a cathode ringhaving an upper portion in which the impregnated pallet is fitted; acathode sleeve containing a heater therein and having a closed upper endmounted to the lower end of the cathode ring such that the closed upperend has a surface in direct contact with a lower surface of theimpregnated pallet, so as to transmit directly the heat from the heateraccumulated in the cathode sleeve to the impregnated pallet; a cathodeholder surrounding the cathode sleeve and having an upper end surface;and means for centering the cathode ring and the cathode holder wherebymetal ribbons are formed integrally with the cathode ring and arefixedly mounted to the upper end surface of the cathode holder.
 2. Animpregnated cathode in accordance with claim 1, wherein the metalribbons comprises a predetermined number of uniformly spaced metalribbons formed integrally with the lower end of the cathode ring, eachmetal ribbon having an end fixed to the closed upper end surface of thecathode holder.